The invention relates to fused silica glass and articles made therefrom. More particularly, the invention relates to fused silica glass having low concentrations of hydroxyl (OH) groups, deuteroxyl (OD) groups, chlorine (Cl), bromine (Br), and fluorine (F). Even more particularly, the invention relates to fused silica glass having low concentrations of the above-mentioned species that lead to low levels of light induced wavefront distortion and polarization induced birefringence.
Optical components used in the semiconductor field, particularly in the area of lithography, have stringent requirements for both dynamic and static properties. Dynamic properties of interest include light induced wavefront distortion (LIWFD), induced absorption (IA), polarization induced birefringence (PIB), and fluence dependent transmission (FDT). Static properties of interest include, among others, refractive index homogeneity (index homogeneity), birefringence, and transmission.
It is difficult for currently available fused silica optical elements to meet index homogeneity requirements for semiconductor lithography applications. In addition, the next generation of lithography optics will require improved LIWFD, PIB, and index homogeneity. Therefore, what is needed is a fused silica glass having improved index homogeneity, light induced wavefront distortion, and polarization induced birefringence.